1. Field of the Invention
The present invention relates to a thermal transfer recording apparatus and a driving method therefor, and more particularly to an improvement in a wind-up apparatus for an ink sheet and a method therefor.
2. Description of the Prior Art
A thermal transfer recording apparatus carrying out polychromatic recording, as disclosed in the Japanese Patent Application Laid-Open No. 58-140266, uses an ink sheet having a plurality of color ink and overlaps each color ink of the sheet onto a recording paper in order, thereby carrying out polychromatic recording.
The ink sheet loaded in this kind of thermal transfer recording apparatus and wound in a rolling manner is drawn out and transported to a transfer unit each time the ink sheet is transferred. In this case, when a slack or a wrinkle is created at the ink sheet while transporting, its transport system is hindered to cause the inconvenience, such as a color shift or an impossible transfer. Hence, in order to apply a proper back tension to the loaded ink sheet, a friction mechanism composed of a friction sheet is provided, the friction mechanism being detailed in the Japanese Patent Application Laid-Open No. 62-41070.
At the above-mentioned apparatus, a wind-up roll for winding the used ink sheet is driven through the same friction mechanism as in the ink sheet feed roll, thereby generating a proper winding force to wind up the ink sheet. The friction mechanism generates a slip to obtain the winding speed meeting the printing transfer speed regardless of a winding diameter varying with the amount of the wound-up ink sheet.
Meanwhile, as disclosed in the Japanese Utility Model Publication No. 03-446, an ink sheet feed device of a printer has been proposed which connects DC motors to a pair of rotary members fixed to both lengthwise ends of the ink sheet so that rotations of both the rotary members are so controlled that the ink sheet delivered from one rotary member is wound up on the other.
The apparatus using the friction mechanism for drawing out and winding up the ink sheet, cannot eliminate particular variation caused by the friction mechanism in the drawing-up tension (back tension) and wind-up tension, and also environmental conditions and abrasion may cause variation in the tension of the ink sheet, which makes a poor transfer caused by wrinkle and an improper transport of the ink sheet.
The apparatus using a pair of DC motors to feed the ink sheet electrically controls the DC motors only by two members of rotations, thereby, creating such problems that the feed speed for the ink sheet varies following variation in a diameter of an ink sheet roll and that the tension applied thereto varies.